FIG. 2.
IFN-γ production by volunteers following ingestion of 4.5 × 108 CFU of live oral typhoid vaccine CVD 908-htrA (high dose), 5 × 107 CFU of CVD 908-htrA (lower dose), or buffer (placebo). PBMC obtained from the volunteers before and 28 days after immunization were evaluated for IFN-γ production in response to STF or BSA (control) as described in Materials and Methods. Results are expressed as mean net picograms per milliliter ± standard errors for all volunteers in each group. The asterisks denote P values of <0.01, as determined by a one-tailed paired t test of postimmunization versus preimmunization values.